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The
ANNEALING
PROCESS

An
easy guide on how to anneal metals

To
define the annealing process in simple terms means to remove
any stresses and return a material to a soft and workable state.

This
is especially so in metals that become work hardened,
like copper and brass, although brass can become very brittle and
fracture
easily.

In
steels, this annealing process is generally used to make
the metal more pliable and less likely to fracture.

This
annealing process can also be used on glass. In other
words, if you have a material that turns liquid upon heating
(disregarding the
temperature for now) then it can be annealed.

How
To
Anneal
Copper

The
copper should be clean and bright, otherwise oxides will
form and become embedded in the surface on heat-up, and should be
warmed up with
a blow-lamp (a kitchen stove will do this at a push) generally rather
than at a
specific point, although copper tends to spread heat quickly through
the metal.

Once
a background heat is produced, when the metal shows
different colours radiating away from the heat source, then you are
looking for
a dark red (plum colour) reaching the part you want annealing
– it’s like the
colours of the rainbow moving from blue through to bright red as the
hottest.

Once
this occurs quickly immerse the copper you are annealing into a
water bath, and that’s it. Job done.

The
easy test is to tap it with a screwdriver or something
similar. If you hear a ringing sound, the copper is still hard and
needs to be
annealed again. If the sound is dull then you have annealed
the copper
properly.

Don’t
delay the quenching too much otherwise you will not
achieve the annealed copper you were aiming for.

Before
you begin to work the copper you must remove any
surface oxides that have formed with a wire brush, wire wool or emery
cloth as
these become embedded, spoiling the appearance, and are difficult to
remove
later.

How
To
Anneal
Brass

Annealing
brass is very similar to copper although the
temperature should be a little cooler.

What
you are looking for as you apply the flame of your
blow-lamp onto the part to be annealed is the tell-tale colours again.

When
the brass starts to show a blackened colour, then is
the time to quench it quickly before cleaning it up.

How
To
Anneal
Aluminium (Aluminum)

Now
here you need to be very careful as the difference in
temperature between softening and melting is marginal.

Clean
up the metal first before coating it with household
soap, directly from the bar, covering the area of the aluminium you
need to
anneal (any brand will do providing it is a solid household soap and
there is
no built in conditioner for dry skin included).

With
your blow-lamp set at a low heat, run it around the
surface, warming the work up generally and make a point of not keeping
your
flame in one place for too long.

Keep
warming it up until you see the soap turning black and
then shut the heat off rapidly and dunk it in water.

Clean
it up and the jobs done...

You
can see here that rather than watching for colours like
on the steel, brass and copper process, the signal is the start of the
burning
of the
soap, meaning it has reached the right temperature.

How
To
Anneal Steel

Annealing
steel is generally needed when you are dealing
with heat hardened steels.

Steel
generally needs to be heated to cherry red and allowed
to cool down naturally, the slower the better.

What
the heating does is to allow the molecules within the
steel to align properly and the slow cooling keeps them aligned, that
way
making the steel more easily worked.

Looking
at a blacksmith and his forge you will see that
while the metal is hot it can be shaped easily with a good clout
because the
molecules are in line. When the work has cooled after being beaten, the
molecules are out of line and the metal is harder and more likely to
fracture.
Obviously the more impacts it receives the harder (and more brittle) it
becomes.

This
is what is known as ‘work hardening’!

How
To
Anneal Stainless Steel

To
anneal stainless steel, basically softening it, requires
a lot more heat (1900°F
/ 1000+°C) than
annealing steel in that an
orangey red colour needs to be achieved with your blow-lamp, but it
also needs
to be kept orange for at least ten minutes – preferably
longer to do it
properly.

It
all depends on the size of the piece of stainless steel
you want to anneal. Larger flat pieces will definitely warp as they
need to be
cooled very quickly to stop the chromium and the carbon bonding
– it’s the
chromium that makes it stainless - so be prepared to have to flatten
the sheet
out. For small sections this is not so much of a problem.

If
you have the option, being left in a kiln for around an
hour at those temperatures then quenching quickly does the best job.